"Investigative efforts have revealed a troubling pattern of behaviour by Tad Cummins, suggesting the 50-year-old may have been abusing his role as a teacher to groom this vulnerable young girl for some time in an effort to lure and potentially sexually exploit her," the agency said in its alert.

"Having now been on the run for more than five days, Cummins may have taken her, frankly, anywhere," the agency said.

On March 13, video surveillance at a Columbia gas station showed Cummins filling up his silver Nissan Rogue.

A short time later, investigators say, he drove to Shoney's restaurant, where Thomas had been dropped off by a friend and was waiting.

Investigators think he manipulated her into leaving with him, but he wasn't authorised to take a minor, and she wasn't old enough to consent.

Then, nothing. After their disappearance, investigators said they had received hundreds of tips from 24 states, but not enough information to tighten the dragnet despite a multi-state manhunt and Cummins' addition to Tennessee's most wanted list.

The Tennessee Bureau of Investigation said Cummins may be keeping Thomas out of sight of authorities, possibly sleeping in his car or in a rural community.

Last month, the agency released new images of Cummins in an effort to keep the case in the spotlight.

The pictures were from a week before Cummins and Thomas disappeared, and show him wearing a camouflage cap and pushing a shopping cart at a store.